junkcltr

iTrader: (1)

GM made the TBI engine for the trucks and camaros. The trucks had non-roller cams. The later camaro with a small cap dizzy had roller cams. If GM intended the roller cam to have a special gear then the TBI small cap dizzy would not be inter-changeable. All of the sources I have say the TBI dizzy is interchangeable.

Overall, it seems to me that the gear on a GM roller and non-roller cam use a cast iron or Austempered iron gear and therefore do not require a melonized gear. Any factory dizzy will work with the GM cams. Only a billet roller with a billet gear require a melonized gear. Any one have any info to disprove this?

1986BANDIT

i know your post is a little old but what did you find out?im building an l31 vortec,i have a gmpp roller cam(baby LT4)and wondered what your findings are,ive also got a tpi small cap dizzy from a roller block(was going to change the gear from it to a vacuum adv dist-hei)

• Camshaft Type (P/N 12677151): Hydraulic roller
• Camshaft Lift (in.): 0.473” intake / 0.473” exhaust
• Camshaft Duration (@.050 in.): 215° intake / 223° exhaust

GeneralDisorder

iTrader: (1)

I beleive all small cap GM distributors have Mellonized gears. They were introduced the same year GM went to roller cams. They are compatible with BOTH types of cams. They are hard for the roller cams and also "slick" allowing them to work with the flat tappet cams also. The Mellonizing process is a special case hardening / nitriding process that leaves a porous outer layer that is very "lubricitous" but also very hard.

I dropped a new small cap unit into my 86 LB9 flat tappet and will be using it on a Comp HR cam in my Vortec when I swap it into the car. Davis Unified Ignition assured me the Mellonized gear will work on both and will not need to changed out between cams.

GD

1986BANDIT

so,you would recommend that i remove the gear from my tpi distributor(small cap hei) and install it on my large cap hei distributor(i need this for carb application with vac advance)?
im getting close to the point were i have the parts i need to put this together,also i wondered if ls "retainers" would work with ls valve springs on vortec heads?im thinking there is a
size difference of the valve stem or keeper but i don't have anything apart yet to check.

GeneralDisorder

iTrader: (1)

Yeah I would say move it over.

The LS springs need a beehive retainer. The Comp 787 retainer is the one for beehives on a Vortec.

GD

maroe624

I went with a brand new AC Delco melonized gear for my [L31]. Just get a new gear and be done. Plus I'm sure that gear has some wear from the last 20 years or so. So you dont want play between cam and gear for sparks sake lol

Fast355

iTrader: (2)

I put a Napa Echlin gear on my L31 distributor when the stock gear wore out at 80K and have run it with both the GM 395' roller cam and a cast core Comp roller. I have also used a new stock GM L31 gear on a non roller cast core Lunati cam in a 305 in my Tahoe. Both of these setups ran more than 40K miles with very little wear on both cam and distributor gears.